Recently, mixed fibers of cellulose fiber and polyester fiber (hereinafter referred to as C/P fibers) have been widely used. In dyeing the mixed fabric, the cellulose fibers are dyed with a water-soluble reactive dye, while the polyester fibers are dyed with a water-insoluble disperse dye. However, the reactive dye and the disperse dye differ each other in dyeing condition.
In some detail, dyeing of cellulose fibers with a reactive dye should be usually carried out in the presence of an acid binding agent, e.g., sodium carbonate, potassium carbonate, sodium hydroxide, etc., and an electrolyte, e.g., sodium chloride, sodium sulfate, etc., under conditions of pH of 10 or more and temperatures of not higher than 100.degree. C. If the pH is too low during the dyeing, reactivity to cellulose fibers (degree of exhaustion) is reduced; and at too high a temperature, the reactive dye undergoes hydrolysis to a failure in satisfactory dyeing.
On the other hand, dyeing of polyester fibers with a disperse dye should be usually carried out under a weakly acidic to neutral condition at a high temperature of about 130.degree. C. If the pH is too high, the disperse dye is hydrolyzed resulting in a failure of satisfactory dyeing; and if the temperature is too low, the degree of exhaustion is greatly reduced.
Therefore, dyeing of C/P fibers has been achieved by a two bath dyeing method, in which a dyeing bath is made weakly acidic to neutral, and polyester fibers are first dyed with a disperse dye at a high temperature of about 130.degree. C., and then cellulose fibers are dyed with a reactive dye at a pH of 10 or higher at a temperature not more than 100.degree. C.
In order to rationalize dyeing conditions, attempts have recently been made to dye C/P fibers with a mixture of a reactive dye and a disperse dye using a mono-bath in a single-stage method. In order to realize these attempts, it is inevitably required to develop a reactive dye which exhibits satisfactory reactivity (degree of exhaustion) without being hydrolyzed even under the conventional dyeing conditions for polyester fibers. However, reactive dye well serving this purpose has not yet been obtained.
Known reactive dyes include, for example, those represented by the following formulae A to C: ##STR1##
Any of these conventional reactive dyes has a disadvantage of seriously low reactivity to cellulose fibers (degree of exhaustion) under the dyeing conditions of a weakly acidic to neutral region and a high temperature of 130.degree. C. and is, therefore, unsuitable as a reactive dye for dyeing C/P fibers according to a mono-bath single-stage dyeing method.